Tires have been fitted with safety inserts which support the tires when there is a puncture or a serious loss of pressure.
However, the life of such a safety insert is limited, and it is therefore generally necessary to provide means for warning the driver of the occurrence of an incident in one of the tires of his vehicle.
A first solution, known in particular from patent application WO94/03338, consists in using systems for detecting one or more modes of resonance characteristic of running of a tire supported by its insert.
A system of this type includes one or more accelerometers, means for filtering the acceleration measurement signals in one or more frequency bands, and processing means which determine from these acceleration measurements characteristic values which are subsequently compared with warning detection thresholds.
Another solution uses safety inserts which include means of voluntarily degrading the vibration behavior of the vehicle during running supported by these inserts. The characteristic vibrations thus generated warn the driver of an abnormal pressure condition in one of his tires, by means of a suitable detection system for example.
In this respect, see U.S. Pat. No. 4,262,724 or U.S. Pat. No. 4,157,726, for example.
Regardless of whether the safety insert does or does not include means for generating a degraded vibration mode, it is desirable that the method used to detect the characteristic signature of running on the safety insert should be capable of allowing for the vibration level of the ground, in order to avoid the triggering of false alarms, particularly when the vehicle is running on rougher roads or tracks.
A first solution for this purpose could consist of determining a characteristic parameter of the vibration level of the ground, for example from acceleration measurements in certain frequency bands, and making the warning detection threshold or thresholds depend on this parameter.
However, a method of this kind would clearly require considerable computing power.